Attribution modelling is the method used to measure the financial effectiveness of a communication channel and the impact this has on business goals.

What is attribution?

Attribution is essentially credit. Each PPC conversion on your website will follow directly from a specific set of targeting criteria.

Suppose your Adwords campaigns have been set up to drive sales of fancy candles for your business. Depending on your Adwords strategy, these could include:

  • [candles for sale online] – Generic search
  • Google Display Network ad – Remarketing
  • [{your brand name} candles] – Brand search

If your customer clicks on one of your Google search or Display Network ads and goes on to convert, providing your tracking is set up and working correctly, Adwords will attribute (or credit) this sale to a specific ad and keyword.

What attribution models do you have to choose from?

In Google Ads there are six attribution models to choose from:

  • Last click
  • Time decay
  • Linear
  • Position based
  • First click
  • Dana driven

Last click

The default model used when setting up a conversion in AdWords is Last Click. This model favours efficiency as you will be able to see the last touch point where the user converted.

Is it the right model to use? Probably not. This model significantly overvalues your branded terms and favours customer recycling.

Time decay

This model is based on exponential decay, assigning the majority of the credit to the last touch point and a lessened value to the earlier touch points.

More complex in that it uses an algorithm to delegate the credit to the correct touch points, looking at the channel closest to the conversion and working backwards.

This model assumes that as the user gets closer and closer to converting, the importance of the channel will increase in line with the intent.


Linear modelling attributes credit to every touch point in the conversion path.

The benefit of this model is that every touch point is considered, so it creates a level playing field where you will be able to see where each and every keyword in your AdWords account attributed to a conversion.

Position based

This model combines the best of Linear and Time Decay, Position-Based Attribution attributes 40% to the first and last touch point and the addition 20% across every touch point in between.

Using this model will allow you to optimise your campaigns and keywords based on the most pivotal points in the conversion process.

First click

This model follows the same premise as Last Click; however, all of the credit is attributed to the First Click.

This model favours the first touch point and will assign 100% of the credit to the first click in the conversion, so if a new user searches for a term > clicks through on paid > returns directly > converts via a social ad – the credit will be attributed to the initial paid ad.

Data driven

This model is the holy grail of attribution models for AdWords, as it gives credit for conversions based on how people search for your business and decide to become your customers.

This model differs to all of the above as it uses your conversion data to calculate the actual contribution of each keyword across the conversion path, making the model completely different for each advertiser.

Short conclusion

While these models might seem a bit confusing, they’re well worth exploring. You may end up with a more accurate picture of which ads are driving your conversions.